In general, a seat of a vehicle is arranged at a vehicle body by a seat slide apparatus for adjusting a position of the seat in a longitudinal direction of the vehicle body. The seat slide apparatus allows the seat to slide along a rail. In particular, the seat slide apparatus is configured so that rollers arranged at the rail therealong roll to adjust the position of the seat in the longitudinal direction of the vehicle body. A known seat slide apparatus (a seat slide apparatus 81 in FIG. 13) is disclosed in JP3678191B (which will be hereinafter referred to as Reference 1).
The seat slide apparatus 81 disclosed in Reference 1 is illustrated in FIG. 13. The seat slide apparatus 81 includes a pair of upper rails 82 adapted to be attached to a lower surface of a seat and a pair of lower rails 83 adapted to be arranged on a floor of a vehicle (the upper rail 82 and the lower rail 83 arranged at one of both sides in a width direction of the seat are shown in FIG. 13). The upper rail 82 is slidable relative to the lower rail 83 in a longitudinal direction thereof. Pairs of rollers 84 are arranged at front and rear ends of the upper rail 82, that is, the four rollers 84 are arranged at the upper rail 82. The rollers 84 guide the upper rail 82 to slide along the lower rail 83. A pair of shoes 85 is arranged in vicinity of the pair of rollers 84 (84a) positioned at the front end of the upper rail 82 and another pair of shoes 85 is arranged in vicinity of the pair of rollers 84 (84b) positioned at the rear end of the upper rail 82, that is, the four shoes 85 are arranged at the upper rail 82. Each of the shoes 85 functions to restrict vibrations between the upper rail 82 and the lower rail 83.
When adjusting a position of the seat in a longitudinal direction of a vehicle body, the rollers 84 guide the upper rail 82 to slide along the lower rail 83; thereby, the position of the seat may be adjusted by a small force. In addition, the vibrations between the upper rail 82 and the lower rail 83 are restricted or absorbed by the shoes 85; therefore, the upper rail 82 is smoothly slidable relative to the lower rail 83.
In the seat slide apparatus 81 disclosed in Reference 1, each of the rollers 84 is arranged at an exterior side of the shoe 85 in a width direction of the upper rail 82 as illustrated in FIG. 13. Therefore, for example, in a case where the lower rail 83 is configured to form a round shape protruding downwardly as shown in FIG. 14, an amount of elastic deformation of the shoe 85 and a sliding load may increase when the upper rail 82 moves through a curved area of the lower rail 83. As a result, the upper rail 82 may not smoothly slide along the lower rail 83.
On the other hand, for example, in a case where the lower rail 83 is configured to form a round shape protruding upwardly as shown in FIG. 15, a sliding load may decrease when the upper rail 82 moves through a curved area of the lower rail 83. At this time, vibrations between the upper rail 82 and the lower rail 83 in a vertical direction thereof may increase; therefore, the stable sliding movement of the upper rail 82 may not be attained. In addition, a position of a seat lock mechanism of the seat slide apparatus 81 may be misaligned in the curved area; therefore, the position of the seat may not be fixed in the longitudinal direction of the vehicle body.
A need thus exists for a seat slide apparatus which is not susceptible to the drawbacks mentioned above.